Pairing, crystallization and string correlations of mass-imbalanced atomic mixtures in one-dimensional optical lattices

We numerically determine the very rich phase diagram of mass-imbalanced binary mixtures of hardcore bosons (or equivalently -- fermions, or hardcore-Bose/Fermi mixtures) loaded in one-dimensional optical lattices. Focusing on commensurate fillings away from half filling, we find a strong asymmetry between attractive and repulsive interactions. Attraction is found to always lead to pairing, associated with a spin gap, and to pair crystallization for very strong mass imbalance. In the repulsive case the two atomic components remain instead fully gapless over a large parameter range; only a very strong mass imbalance leads to the opening of a spin gap. The spin-gap phase is the precursor of a crystalline phase occurring for an even stronger mass imbalance. The fundamental asymmetry of the phase diagram is at odds with recent theoretical predictions, and can be tested directly via time-of-flight experiments on trapped cold atoms.Comment: 4 pages, 4 figures + Supplementary Materia

Gamma Rays from Compton Scattering in the Jets of Microquasars: Application to LS 5039

Recent HESS observations show that microquasars in high-mass systems are sources of VHE gamma-rays. A leptonic jet model for microquasar gamma-ray emission is developed. Using the head-on approximation for the Compton cross section and taking into account angular effects from the star's orbital motion, we derive expressions to calculate the spectrum of gamma rays when nonthermal jet electrons Compton-scatter photons of the stellar radiation field. Calculations are presented for power-law distributions of nonthermal electrons that are assumed to be isotropically distributed in the comoving jet frame, and applied to $\gamma$-ray observations of LS 5039. We conclude that (1) the TeV emission measured with HESS cannot result only from Compton-scattered stellar radiation (CSSR), but could be synchrotron self-Compton (SSC) emission or a combination of CSSR and SSC; (2) fitting both the HESS data and the EGRET data associated with LS 5039 requires a very improbable leptonic model with a very hard electron spectrum. Because the gamma rays would be variable in a leptonic jet model, the data sets are unlikely to be representative of a simultaneously measured gamma-ray spectrum. We therefore attribute EGRET gamma rays primarily to CSSR emission, and HESS gamma rays to SSC emission. Detection of periodic modulation of the TeV emission from LS 5039 would favor a leptonic SSC or cascade hadron origin of the emission in the inner jet, whereas stochastic variability alone would support a more extended leptonic model. The puzzle of the EGRET gamma rays from LS 5039 will be quickly solved with GLAST. (Abridged)Comment: 17 pages, 11 figures, ApJ, in press, June 1, 2006, corrected eq.

Controlling ultracold atoms in multi-band optical lattices for simulation of Kondo physics

We show that ultracold atoms can be controlled in multi-band optical lattices through spatially periodic Raman pulses for investigation of a class of strongly correlated physics related to the Kondo problem. The underlying dynamics of this system is described by a spin-dependent fermionic or bosonic Kondo-Hubbard lattice model even if we have only spin-independent atomic collision interaction. We solve the bosonic Kondo-Hubbard lattice model through a mean-field approximation, and the result shows a clear phase transition from the ferromagnetic superfluid to the Kondo-signet insulator at the integer filling.Comment: 4 pages, 2 figure

Transcriptional analysis of temporal gene expression in germinating Clostridium difficile 630 endospores.

Clostridium difficile is the leading cause of hospital acquired diarrhoea in industrialised countries. Under conditions that are not favourable for growth, the pathogen produces metabolically dormant endospores via asymmetric cell division. These are extremely resistant to both chemical and physical stress and provide the mechanism by which C. difficile can evade the potentially fatal consequences of exposure to heat, oxygen, alcohol, and certain disinfectants. Spores are the primary infective agent and must germinate to allow for vegetative cell growth and toxin production. While spore germination in Bacillus is well understood, little is known about C. difficile germination and outgrowth. Here we use genome-wide transcriptional analysis to elucidate the temporal gene expression patterns in C. difficile 630 endospore germination. We have optimized methods for large scale production and purification of spores. The germination characteristics of purified spores have been characterized and RNA extraction protocols have been optimized. Gene expression was highly dynamic during germination and outgrowth, and was found to involve a large number of genes. Using this genome-wide, microarray approach we have identified 511 genes that are significantly up- or down-regulated during C. difficile germination (p≤0.01). A number of functional groups of genes appeared to be co-regulated. These included transport, protein synthesis and secretion, motility and chemotaxis as well as cell wall biogenesis. These data give insight into how C. difficile re-establishes its metabolism, re-builds the basic structures of the vegetative cell and resumes growth

A PRELIMINARY INVESTIGATION INTO THERMAL SPRAY AND OTHER METAL/POLYMER DEPOSITION PROCESSES AND THEIR POTENTIAL USE IN THE OIL INDUSTRY

Polymeric coatings are being used in a raising number of applications, contributing to protection against weather conditions and localized corrosion, also reducing erosion wear. The coatings may be deposited by various processes and thermal spray is being recently investigated as a new alternative. This paper reports an exploratory study into various polymer deposition processes and evaluates their influence on the quality of the produced coating, concerning dispersion, cohesiveness and adhesion onto steel substrates. Different content aluminum/MDPE (medium density polyethylene) mixtures and processing parameters were studied as an attempt to identify the most promising parameters regarding their future application to produce coatings for the oil industry. The material characterization was carried out via mechanical testing (ASTM D638). The coating adhesion was evaluated by bend and ASTM C633-79 tensile tests. A microscopy evaluation of the coatings was also carried out. The produced films showed low friction surfaces and adequate adhesion to steel substrates. The presence of MAN (maleic anhydride) in the composite was responsible for the MDPE to recover its ductility, with a small increase of strength and rigidity, as well as a significant enhancement of coating adhesion to substrate

Correlations in the low-temperature phase of the two-dimensional XY model

Monte Carlo simulations of the two-dimensional XY model are performed in a square geometry with fixed boundary conditions. Using a conformal mapping it is very easy to deduce the exponent eta_sigma(T) of the order parameter correlation function at any temperature in the critical phase of the model. The temperature behaviour of eta_sigma(T) is obtained numerically with a good accuracy up to the Kosterlitz-Thouless transition temperature. At very low temperatures, a good agreement is found with Berezinskii's harmonic approximation. Surprisingly, we show some evidence that there are no logarithmic corrections to the behaviour of the order parameter density profile (with symmetry breaking surface fields) at the Kosterlitz-Thouless transition temperature.Comment: 7 pages, 2 eps figure

1/2-Anyons in small atomic Bose-Einstein condensates

We discuss a way of creating, manipulating and detecting anyons in rotating Bose-Einstein condensates consisting of a small number of atoms . By achieving a quasidegeneracy in the atomic motional states we drive the system into a 1/2--Laughlin state for fractional quantum Hall bosons. Localized 1/2--quasiholes can be created by focusing lasers at the desired positions. We show how to manipulate these quasiholes in order to probe directly their 1/2--statistics.Comment: 4 pages, 3 figure

Occupational Diseases and Perceived Health in Operating Room Nurses : A Multicenter Cross-Sectional Observational Study

Background: The surgical environment has multiple factors that could affect nurses' health. The aim was to determine the effects of the working environment of operating room nurses on their health compared to hospitalization nurses. Methods: A sample of operating room nurses and hospitalization nurses were included in the study and participated by filling in a self-report survey containing sociodemographic data items, the validated Nordic and SF12 scales and a list of medical conditions. Results: Three hundred and thirty-one nurses participated in the study. Statistically significant results had obtained for diagnoses of musculoskeletal disorders and contact dermatitis among the operating room nurses. Conclusion/Application to Practice: Continuous training in ergonomics is essential. Moreover, surgical protocols for preventing infection should be revised, optimizing the chlorhexidine content of soaps to reduce the risk of lesions among the surgical staff